Abstract : Guided optics spectrometers can be essentially classified into two main families:
based on Fourier transform or dispersion. In the first case, an interferogram generated inside
an optical waveguide and containing the spectral information is sampled using spatially
distributed nanodetectors. These scatter quasi-non-perturbingly light into the detector that is
in contact with the waveguide, helping to reconstruct the stationary wave. A dedicated FFT
processing is needed in order to recover the spectrum with high resolution but limited spectral
range. Another way is to directly disperse the different wavelengths to different pixels, either
introducing differential optical path in the same propagation plane (multiple Mach-Zehnder
interferometers or Arrayed Waveguides Gratings), or using a periodic structure to
perpendicularly extract the optical signal confined in a waveguide (photonic crystals or
surface gratings), and by means of a relay optics, generate the spectrum on the Fourier plane
of the lens, where the detector is placed. Following this second approach, we present a laserfabricated
high-resolution compact dispersive spectro-interferometer (R>2500, 30nm spectral
range at λ = 1560nm), using four parallel waveguides that can provide up to three nonredundant
interferometric combinations. The device is based on guided optics technology
embedded in bulk optical glass. Ultrafast laser photoinscription with 3D laser index
engineering in bulk chalcogenide Gallium Lanthanium Sulfide glass is utilized to fabricate
large mode area waveguides in an evanescently-coupled hexagonal multicore array
configuration, followed by subsequent realization of nanoscaled scattering centers via one
dimensional nanovoids across the waveguide, written in a non-diffractive Bessel
configuration. A simple relay optics, with limited optical aberrations, reimages the diffracted
signal on the focal plane array, leading to a robust, easy to align instrument.